Serotonin enhances excitability in neostriatal neurons by reducing voltage-dependent potassium currents.
The physiological effects of serotonin (5-HT) on rat neostriatal neurons were investigated using current-clamp techniques in neostriatal slices and voltage-clamp techniques in acutely dissociated adult neostriatal neurons. In most neurons (35/51), bath-applied 5-HT (10-60 microM) decreased the first spike latency and increased the evoked firing frequency. Membrane input resistance was also increased in most neurons (33/35) but could not explain the enhanced responsiveness. Tetrodotoxin, at concentrations sufficient to block spike production, did not block the ability of 5-HT to enhance the slow ramp-like voltage trajectory produced by depolarizing current injection. The role of potassium currents in the 5-HT effect was examined using whole cell voltage-clamp; in 6 of 9 neurons, 5-HT reversibly decreased inactivating potassium currents activated by depolarization. These experiments suggest that 5-HT's effect on the ramp trajectory may be mediated by a reduction of potassium currents activated by sub-threshold depolarization.
Stefani
A
A
Department of Anatomy and Neurobiology, College of Medicine, University of Tennessee, Memphis 38163.
Surmeier
D J
DJ
Kitai
S T
ST
D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects / Q000502:physiology*; D005071:Evoked Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D051381:Rats; D012701:Serotonin / Q000494:pharmacology*; D013779:Tetrodotoxin / Q000494:pharmacology
D015221:Potassium Channels; D012701:Serotonin; D013779:Tetrodotoxin